If your PNG file already has a transparency then that transparency will work.
Import the PNG file into your project.
Drag it from the bin onto the stage which will automatically create a picture player.
Set the blend to transparent.
Set the layer to a higher number than anything else
Reposition it to where you want it.

You're right! everythings works fine! But in my main project i use Scaller to stretch Images to screen edges. And I found when i use scaller, transparent areas becames unusial(see attachments, I marked these areas, by arrows),

I am just curious if the problem @Mark identified with transparent PNG files has been fixed in V245b16 ?

I am getting some recurring irregular drop out of image information when using PNG transparency through Picture Player and 3D Rect Project. The image segments are layered and slightly offset / rotated. There are 4 x transparent PNG files that make up the attached screengrabbed image that are rendered to a Virtual Stage located in a control scene. The image appears complete for a number of activations and displays with irregular dropout for others. I have added the FFGLPremultiply between the Picture Players and the 3D Rect Project actors however the irregular dropout appears to persist.